Vacuum packaging machines of a known type comprise a vacuum chamber arranged to receive unsealed product packages and operable to perform a vacuum sealing operation on the product packages. Typically the product packages contain products such as meat cuts, arranged in a bag formed by a heat-shrinkable film. After loading and closing the vacuum chamber, the vacuum sealing operation normally comprises vacuumisation, sealing the mouth of the vacuumised bags, and reintroducing air into the chamber. Then the chamber is opened and the vacuum chamber is unloaded. The product packages may then generally be conveyed to a heat-shrinking unit, typically a hot water tunnel, dip tank, hot air tunnel, or other shrink activating system.
In conventional conveyorised chamber systems, the vacuumisation step typically takes at least 20-30 seconds which is significant processing time in the overall packaging process. During this time, the only step which can be taken is to prepare the next product packages for loading into the vacuum chamber, for example by conveying them onto an infeed conveyor. Accordingly, the vacuum packaging machine may cause a bottle-neck in the overall packaging process.
Rotary vacuum packaging machines are known, which comprise a series of vacuum chambers and chain driven product platens. In operation of the machine the platens move from a loading position, thorough a vacuum/sealing/venting stage, to an unloading position, and finally back to the loading position. One disadvantage of these machines is that they have a large footprint, in the order of about 17 m2 for example, and therefore take up a large amount of floor space. A further problem is that these machines generally require manual loading and bag spreading and are thus difficult to incorporate in a fully automated process.
One way of reducing the bottle-neck caused by the vacuum packaging machine is to configure the vacuum packaging machine to heat seal a product package containing two products and cut between the products to form two separated product packages. Such a configuration is described in WO01/56888. This configuration is limited to making pairs of product packages of the same length.
It is an object of at least a preferred embodiment of the present invention to provide a vacuum packaging machine which is suited for use in an automated production line and addresses at least one of the abovementioned disadvantages, or which at least provides the public with a useful choice.